U.S. patent application number 13/031360 was filed with the patent office on 2012-08-23 for fiber tow treatment apparatus and system.
This patent application is currently assigned to UNITED STATES COUNCIL FOR AUTOMOTIVE RESEARCH. Invention is credited to Jeffrey Scott Dahl, Charles William Knakal, Bhavesh Suresh Shah, Chen-Shih Wang.
Application Number | 20120213997 13/031360 |
Document ID | / |
Family ID | 46605134 |
Filed Date | 2012-08-23 |
United States Patent
Application |
20120213997 |
Kind Code |
A1 |
Wang; Chen-Shih ; et
al. |
August 23, 2012 |
FIBER TOW TREATMENT APPARATUS AND SYSTEM
Abstract
In one embodiment, a fiber treatment system includes a rotatable
nubbed roller including an axis of rotation, a surface, and a
number of spaced apart nubs projecting away from the surface, the
number of spaced apart nubs imparting a number of spaced apart
openings in a fiber tow. In another embodiment, the fiber treatment
system further includes an optionally rotatable spreader roller for
flattening the fiber tow. In yet another embodiment, the loosened,
but still continuous fiber tow is chopped by a downstream chopper
to form short fibers with reduced tow sizes.
Inventors: |
Wang; Chen-Shih; (Troy,
MI) ; Knakal; Charles William; (Grosse Ile, MI)
; Dahl; Jeffrey Scott; (Livonia, MI) ; Shah;
Bhavesh Suresh; (Troy, MI) |
Assignee: |
UNITED STATES COUNCIL FOR
AUTOMOTIVE RESEARCH
Southfield
MI
|
Family ID: |
46605134 |
Appl. No.: |
13/031360 |
Filed: |
February 21, 2011 |
Current U.S.
Class: |
428/398 ; 28/282;
428/364 |
Current CPC
Class: |
B65H 2701/31 20130101;
Y10T 428/2913 20150115; B65H 51/005 20130101; D01G 1/04 20130101;
Y10T 428/2975 20150115; D02J 1/18 20130101; B65H 2701/38 20130101;
B29K 2307/04 20130101; B29C 70/12 20130101; D01D 11/02 20130101;
B29K 2105/12 20130101 |
Class at
Publication: |
428/398 ; 28/282;
428/364 |
International
Class: |
D01D 11/02 20060101
D01D011/02; D02J 1/18 20060101 D02J001/18 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] The present invention was made with Government support under
Department of Energy Cooperative Agreement No. DE-FC26-02OR22910.
The Government has certain rights to the invention.
Claims
1. An apparatus for treating fiber tow, comprising: a rotatable
nubbed roller including an axis of rotation, a surface, and a
number of spaced apart nubs projecting away from the surface, the
rotatable nubbed roller imparting a number of openings on a fiber
tow via penetration of the fiber tow by the number of spaced apart
nubs.
2. The apparatus of claim 1, wherein the number of spaced apart
nubs are formed of a first material and the surface is formed of a
second material different from the first material.
3. The apparatus of claim 2, wherein the first material includes a
polymeric material.
4. The apparatus of claim 1, wherein the number of spaced apart
nubs are integral to the surface.
5. The apparatus of claim 1, wherein the number of spaced apart
nubs are detachable from the surface.
6. The apparatus of claim 1, wherein the number of spaced apart
nubs are uniformly positioned along the axis of rotation.
7. The apparatus of claim 1, wherein the number of spaced apart
nubs are non-uniformly positioned along the axis of rotation.
8. The apparatus of claim 1, wherein the number of spaced apart
nubs are uniformly positioned along a cross-sectional parameter
perpendicular to the axis of rotation.
9. The apparatus of claim 1, wherein one or more of the number of
spaced apart nubs include one or more edges.
10. The apparatus of claim 9, wherein the one or more edges are not
parallel to the axis of rotation.
11. The apparatus of claim 1, wherein one or more of the number of
spaced apart nubs include one or more points per nub for
penetrating the fiber tow.
12. The apparatus of claim 11, wherein the one or more points are
part of a generally cone or pyramid shaped portion of the
corresponding nub.
13. The apparatus of claim 11, wherein the one or more of the
number of spaced apart nubs include two or more points aligned in a
direction not parallel to the axis of rotation.
14. The apparatus of claim 1, wherein the surface is generally
cylindrical.
15. A fiber tow comprising: a number of fiber filaments including
spaced apart openings, at least a portion of the spaced apart
openings being each bounded by two fiber filaments of the fiber
tow.
16. The fiber tow of claim 15, at least a portion of the spaced
apart openings have an average diameter of 1 to 20 millimeters.
17. The fiber tow of claim 15, wherein at least a portion of the
spaced apart openings are non-uniformly positioned relative to each
other.
18. A fiber tow composition comprising: a first number of fiber
tows having a first average tow width and tow weight; and a second
number of fiber tows having a second average tow width and tow
weight, at least one of the tow width and tow weight is different
between the first and second pluralities of fiber tows.
19. The fiber tow composition of claim 18, wherein the first
average tow width is different from the second average tow
width.
20. The fiber tow composition of claim 18, wherein the first
average tow weight is different from the second average tow weight.
Description
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to fiber tow treatment
apparatus and system, and particularly fiber tow treatment
apparatus and system for making fiber reinforced polymer
composites.
[0004] 2. Background Art
[0005] Fiber reinforced polymer composites have been used to
provide lightweight engineering structures. The use of existing
fiber reinforced polymer composites may be limited due to
prohibitive costs associated with the production of fibers suitable
for forming the composites.
SUMMARY
[0006] In one embodiment, a fiber tow treatment system includes a
rotatable nubbed roller including an axis of rotation, a base
having a surface, and a number of spaced apart nubs projecting from
the surface, the spaced apart nub imparting spaced apart openings
in a fiber tow. In certain instances, at least a portion of the
openings are discrete openings spaced apart from each other. In
certain other instances, the spaced apart nubs may be arranged as a
readily detachable piece relative to the base of the rotatable
nubbed roller. In yet certain other instances, the spaced apart
nubs and the surface of the base are of different metallic or
non-metallic materials. In yet certain other instances, the spaced
apart nubs include a polymeric material. In certain other
instances, the spaced apart nubs are integral to the base. In
certain other instances, the spaced apart nubs are non-uniformly
positioned along the axis of rotation.
[0007] In another embodiment, the fiber treatment system further
includes a spreader roller upstream of the rotatable nubbed roller
for flattening the fiber tow. The spreader roller is optionally
rotatable.
[0008] In yet another embodiment, the fiber treatment system
further includes a second and/or third spreader roller upstream of
the rotatable nubbed roller, the second and/or third spreader
roller is optionally rotatable.
[0009] In yet another embodiment, the fiber treatment system
further includes a second rotatable nubbed roller downstream of the
spreader roller.
[0010] In yet another embodiment, the fiber treatment system
further includes a chopping station downstream of the rotatable
nubbed roller for chopping the loosened fibers tows to produce
chopped fibers with reduced tow sizes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1A1 depicts a cross-sectional view of a fiber treatment
system according to one embodiment;
[0012] FIG. 1A2 depicts a perspective view of a non-limiting
example of a rotatable nubbed roller employed in the fiber
treatment system of FIG. 1A1;
[0013] FIG. 1B depicts a cross-sectional view of a fiber treatment
system according to another embodiment;
[0014] FIG. 1C depicts a cross-sectional view of a fiber treatment
system according to yet another embodiment;
[0015] FIG. 2A depicts an expanded top view of a nubbed roller in a
fiber treatment system according to yet another embodiment;
[0016] FIG. 2B depicts an expanded top view of a nubbed roller in a
fiber treatment system according to yet another embodiment;
[0017] FIGS. 3A to 3D depict variable forms and arrangements of the
spaced apart nubs according to yet another embodiment;
[0018] FIG. 4 depicts tensile strength values as a function of
fiber tow sizes according to one example described herein;
[0019] FIG. 5A depicts a fiber treatment system according to
another example described herein;
[0020] FIG. 5B depicts a fiber treatment system according to yet
another example described herein;
[0021] FIGS. 6A1 and 6A2 depict analysis values in relation to the
fiber treatment system of FIG. 5A;
[0022] FIGS. 6B1 and 6B2 depict analysis values in relation to the
fiber treatment system of FIG. 5B;
[0023] FIGS. 7A and 7B depict various analysis values according to
yet another example described herein; and
[0024] FIGS. 8A and 8B depict non-limiting examples of the fiber
treatment system according to yet another embodiment.
DETAILED DESCRIPTION
[0025] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention.
[0026] Except where expressly indicated, all numerical quantities
in this description indicating amounts of material or conditions of
reaction and/or use are to be understood as modified by the word
"about" in describing the broadest scope of the present
invention.
[0027] The description of a group or class of materials as suitable
for a given purpose in connection with one or more embodiments of
the present invention implies that mixtures of any two or more of
the members of the group or class are suitable. Description of
constituents in chemical terms refers to the constituents at the
time of addition to any combination specified in the description,
and does not necessarily preclude chemical interactions among
constituents of the mixture once mixed. The first definition of an
acronym or other abbreviation applies to all subsequent uses herein
of the same abbreviation and applies mutatis mutandis to normal
grammatical variations of the initially defined abbreviation.
Unless expressly stated to the contrary, measurement of a property
is determined by the same technique as previously or later
referenced for the same property.
[0028] In one or more embodiments, a fiber treatment system is
provided to effect the production of cost effective fiber tows with
tow sizes suitable for forming fiber reinforced polymer composites
having desired physical properties. In particular, the fiber
treatment system produces loosened fiber tows ready to be chopped
to form chopped, shorter fibers with reduced fiber tow sizes.
Non-limiting examples of the fibers include carbon fibers, glass
fibers, polymer fibers, natural fibers or combinations thereof.
[0029] In one or more embodiments, the term "fiber tow" may refer
to a fiber bundle of fiber filaments, optionally adhered or
connected to each other. The fiber filaments may be adhered or
connected to each other via a polymer and/or resin coating. The
term "fiber tow size" may refer to a cross-sectional dimension of
the fiber tow measured in a total number of fiber filaments. A 50K
fiber tow, for instance, refers to a fiber bundle of about 50,000
fiber filaments grouped together.
[0030] Fibers such as carbon fibers with smaller tow sizes may be
significantly more expensive to produce due to relatively lower
production throughput and higher energy consumption per equal
weight of manufactured fiber. Attempts have been made to
mechanically split or separate lower cost, large tow fibers and
re-spool them into smaller tow products for downstream
applications. The tow splitting process, however, requires
specialized equipment and may be complicated by frequent occurrence
of twisting of the long continuous fiber tows. Consequently, using
chopped fibers derived from these mechanically split small tow
fibers is cost inefficient in general and retards the effective use
of resultant fiber-containing products such as fiber reinforced
polymer composites.
[0031] In one or more embodiments, the fiber treatment system
includes a rotatable nubbed roller having thereupon spaced apart
protruding nubs. Fiber tows may be pressed against the spaced apart
nubs to be penetrated and to create spaced apart openings within
the fiber tows. As a result, the fiber tows are opened or loosened
due to the formation of these spaced apart openings. The loosened
fiber tows may be subsequently chopped and chopping allows fiber
tows to naturally break apart to form chopped fibers with reduced
tow sizes. The fiber tows are merely loosened without having to be
carefully separated and organized into individual spools. The fiber
treatment system, according to one or more embodiments, therefore
provides a simple and cost effective way of producing fibers for
certain fiber reinforced composite applications.
[0032] In one or more embodiments, the spaced apart nubs may be
varied in pattern and/or shape to accommodate particular needs of a
fiber treatment project. In certain instances, the spaced apart
nubs are arranged non-uniformly and randomly. In certain instances,
the fiber tows can be loosened or opened in a random fashion,
which, when coupled with subsequent chopping, helps provide a
population of chopped fibers with randomized cross-sectional sizes
suitable for certain composite making processes requiring low
viscosity of fiber-resin mixtures, enabling the production of
desired high performance composites.
[0033] In one or more embodiments, the spaced apart nubs may be
arranged as a detachable piece that is readily attachable to the
base of the rotatable nubbed roller or any of the fiber rollers
such as a spreader roller 104 described herein. Thus, a simpler and
more versatile system and hence greater economic efficiency may be
achieved.
[0034] In one embodiment, and as depicted in FIG. 1A1 and FIG. 1A2,
a fiber treatment system generally shown at 100 includes a
rotatable nubbed roller 102 including an axis of rotation A-A' for
loosening a fiber tow 110. The rotatable nubbed roller 102 includes
a base 102a having a surface 114 and a number of spaced apart nubs
102b projecting from the surface 114. The spaced apart nubs 102b
impart spaced apart openings 116 in the fiber tow 110 to form
loosened fiber tow 112. In certain instances, and as depicted in
FIG. 1A2, the surface 114 has a generally cylindrical shape, and
the rotatable nubbed roller 102 has a pair of opposing ends 120,
122 with the surface extending there between.
[0035] In another embodiment, and as depicted in FIG. 1B, the fiber
treatment system 100 may further include a spreader roller 104 for
flattening the fiber tow 110 prior to being loosened via the
rotatable nubbed roller 102. The spreader roller 104 may be
presented with a smooth surface. Without wanting to be limited to
any particular theory, it is believed that the flattening step at
104 helps increase the surface contact between the fiber tow 110
and the spaced apart nubs 102b of the rotatable nubbed roller 102.
The increased surface contact, in turn, results in greater opening
formation and better loosening of the fibers per unit weight of the
fiber tow 110, and hence a population of more individualized fibers
upon chopping.
[0036] Although one spreader roller 104 and one rotatable nubbed
roller 102 are depicted in FIG. 1B, it is operable within the
spirit of the present invention to employ two or more spreader
rollers 104 in a serial relationship upstream of the nubbed roller
102, such as in a system illustrated in FIG. 1C, or to employ two
or more rotatable nubbed rollers 102 downstream of the spreader
roller 104. Alternatively, the spreader rollers 104 and the
rotatable nubbed rollers 102 may mix and match in any suitable
order as long as at least one spreader roller 104 is positioned
upstream of at least one nubbed roller 102.
[0037] In yet another embodiment, and as depicted in FIG. 1C, three
individual spreader rollers 104a, 104b, and 104c are positioned
upstream of the rotatable nubbed roller 102. At least one of the
spreader rollers 104a, 104b, and 104c are each optionally
rotatable. In particular, spreader roller 104b is positioned below
the spreader roller 104a to help effect a downward pulling and
resultant flattening of the fiber tow. The spreader roller 104c is
positioned above the spreader roller 104b to help effect an upward
pulling and further flattening of the previously flattened fiber
tow coming out of the spreader roller 104b. This non-limiting
spacing arrangement of the spreader rollers 104a, 104b, 104c is
believed to effectively assist with the fiber flattening and
spreading as one or more of these spreader rollers may rotate about
their respective shaft and do not necessarily provide much pulling
on their own.
[0038] In yet another embodiment, the fiber treatment system 100
further includes a chopping station formed of a pulling roller 108,
a pinching roller set 118a and 118b, and a chopper 120. In
operation, the pulling roller 108 and the pinching roller set 118a
and 118b together effect pulling of the loosened fiber tow 112
toward the chopper 120. The loosened fiber tow 112 is then chopped
to certain pre-determined length via chopper 120. In particular
instances, and as depicted in FIG. 1C, cutting blades may be
positioned on the outer surface of the chopper 120 and effect fiber
cutting via contact with the outer surface of the pulling roller
108. However, any other suitable chopping stations may be used to
effect the chopping of the loosening fiber tow 112.
[0039] FIG. 2A depicts a non-limiting pattern of the spaced apart
nubs 102b in an expanded top view, wherein the fiber tow 110 is
shown being rolled toward the spaced apart nubs 102b in a rolling
direction and being pressed against the spaced apart nubs 102b to
form a loosened fiber tow 112 including corresponding spaced apart
openings 116. At least a portion of the openings 116 are discrete
relative to each other to effect loosening of the surrounding fiber
filaments while still keeping the entire fiber tow 112 together as
one not-yet-separated entity. The loosened, but still continuous,
fiber tow 112 then gets pulled into the chopper and chopped. The
chopping motion naturally breaks up the fiber tow 112 into smaller
tow sized chopped fibers. One benefit of this arrangement is that
the resultant loosened fiber tow 112 gets chopped immediately after
loosening instead of being collected as individual smaller fiber
tow spools as an extra processing step. Accordingly, the present
invention provides a cost effective way of forming chopped fibers
and fiber composites using the same.
[0040] The spaced apart nubs 102b may be formed integral of the
base 102a, for instance, as a natural structure extension from the
base 102a. In certain instances, the spaced apart nubs 102b and the
base 102a may be formed from the same metallic and/or non-metallic
material. Alternatively, the spaced apart nubs 102b may be
detachable relative to the base 102a. In certain other instances,
the spaced part portions 102b and the base 102a may be formed of
different materials. In certain particular instances, the spaced
apart nubs 102b may include a polymeric material such as
thermoplastic polymer or thermoset polymer, including rubber. In
certain other particular instances, the spaced apart nubs 102b
together form a network of discrete piece of rubber material with
protruding extensions. To further provide versatility and cost
efficiency, the number of spaced apart nubs 102b may be presented
in the form of a discrete piece readily attachable and detachable
to any one of the existing spreader rollers 102a to perform opening
and loosening of the fibers.
[0041] In certain instances, and as depicted in FIG. 2B, the spaced
apart nubs generally shown at 102b may be non-uniformly aligned
along a rolling direction with arrow shown. For instance, a space
distance "d1" between two adjacent protrusions at line L1 is
different from a space distance "d2" between two adjacent
protrusions at line L2. Space distances "d1" and "d2" may each
independently differ from a space distance "dn" between two
adjacent protrusions at line Ln. In certain other instances,
similar non-uniform arrangement can also be independently applied
to the spaced apart nubs 102b along a direction different from the
rolling direction, such as a direction traversal to the rolling
direction.
[0042] Moreover, and to introduce additional non-uniformity or
randomness in the arrangement of the spaced apart nubs 102b, the
nubs can be of different shapes, with non-limiting examples thereof
including needles, triangles, or combinations thereof. For
instance, and as depicted in FIG. 3A, the nubs 102b may have a
cross-sectional shape of a triangle 304 with a point 302 for
imparting openings in the fiber tows. As depicted in FIG. 3B, the
nubs 102b may have a cross-sectional shape of a triangle 308 with a
point 306 for imparting openings and a raised bottom 310. As
depicted in FIG. 3C, the nubs 102b may have a cross-sectional shape
of two connected triangles 314 with points 312 for imparting
openings and a raised bottom 316 for height adjustment. In these
illustrated arrangements, the portions of the nubs 102b which have
a cross-sectional shape of a triangle 304, 308, 314 may be in
three-dimension of the form of a cone or a pyramid as illustrated
in FIG. 3D. In certain instances, one or more of the edges 318,
320, 322, 324, 326 are not parallel to a plane in line with and/or
defined by any one of the opposing ends 120, 122 of the rotatable
nubbed roller 102. In certain other instances, the two or more
points 312 per nub 102b are aligned in a direction not parallel to
the rolling direction.
[0043] In certain instances, 90 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow width
in the range of 4 to 10 millimeters. In certain other instances, 80
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow width in the range of 4 to 9 millimeters. In
yet certain other instances, 70 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow width
in the range of 4 to 8 millimeters. In yet certain other instances,
60 percent of the chopped fiber produced from the loosened fiber
tow 112 has an average tow width in the range of 4 to 7
millimeters. In yet certain other instances, 40 percent of the
chopped fiber produced from the loosened fiber tow 112 has an
average tow width in the range of 4 to 6 millimeters. In yet
certain other instances, 30 percent of the chopped fiber produced
from the loosened fiber tow 112 has an average tow width in the
range of 4 to 5 millimeters.
[0044] In yet certain other instances, 20 percent of the chopped
fiber produced from the loosened fiber tow 112 has an average tow
width in the range of 9 to 10 millimeters. In yet certain other
instances, 30 percent of the chopped fiber produced from the
loosened fiber tow 112 has an average tow width in the range of 8
to 10 millimeters. In yet certain other instances, 50 percent of
the chopped fiber produced from the loosened fiber tow 112 has an
average tow width in the range of 7 to 10 millimeters. In yet
certain other instances, 60 percent of the chopped fiber produced
from the loosened fiber tow 112 has an average tow width in the
range of 6 to 10 millimeters. In yet certain other instances, 80
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow width in the range of 5 to 10
millimeters.
[0045] In certain instances, 90 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow weight
of 15 to 65 milligrams per inch. In yet certain instances, 85
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow weight of 15 to 60 milligrams per inch. In
certain instances, 80 percent of the chopped fiber produced from
the loosened fiber tow 112 has an average tow weight of 15 to 55
milligrams per inch. In yet certain instances, 70 percent of the
chopped fiber produced from the loosened fiber tow 112 has an
average tow weight of 15 to 50 milligrams per inch. In yet certain
instances, 55 percent of the chopped fiber produced from the
loosened fiber tow 112 has an average tow weight of 15 to 45
milligrams per inch. In yet certain instances, 40 percent of the
chopped fiber produced from the loosened fiber tow 112 has an
average tow weight of 15 to 40 milligrams per inch. In yet certain
instances, 35 percent of the chopped fiber produced from the
loosened fiber tow 112 has an average tow weight of 15 to 35
milligrams per inch. In yet certain instances, 25 percent of the
chopped fiber produced from the loosened fiber tow 112 has an
average tow weight of 15 to 30 milligrams per inch. In yet certain
instances, 20 percent of the chopped fiber produced from the
loosened fiber tow 112 has an average tow weight of 15 to 25
milligrams per inch. In yet certain instances, 15 percent of the
chopped fiber produced from the loosened fiber tow 112 has an
average tow weight of 15 to 20 milligrams per inch.
[0046] In certain instances, 90 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow weight
of 20 to 65 milligrams per inch. In certain other instances, 80
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow weight of 25 to 65 milligrams per inch. In
yet certain other instances, 70 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow weight
of 30 to 65 milligrams per inch. In yet certain other instances, 60
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow weight of 40 to 65 milligrams per inch. In
yet certain other instances, 55 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow weight
of 45 to 65 milligrams per inch. In yet certain other instances, 40
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow weight of 50 to 65 milligrams per inch. In
yet certain other instances, 20 percent of the chopped fiber
produced from the loosened fiber tow 112 has an average tow weight
of 55 to 65 milligrams per inch. In yet certain other instances, 15
percent of the chopped fiber produced from the loosened fiber tow
112 has an average tow weight of 60 to 65 milligrams per inch.
[0047] Having generally described this invention, a further
understanding can be obtained by reference to certain specific
examples which are provided herein for purposes of illustration
only and are not intended to be limiting unless otherwise
specified.
Example
[0048] FIG. 4 illustrates fiber composite tensile strength as a
function of fiber tow size (number of fiber filaments in a fiber
tow). As depicted in FIG. 4, the tensile strength of fiber
composites increases from 85 MPa to 270 MPa as the fiber tow size
decreases from 12 K to 0.5 K. An improvement in strength
reinforcement may be attributed to better wet-out and dispersion of
the smaller tow fibers in the resin matrix. This example
demonstrates that fibers at certain tow size such as a tow size
larger than 12K provides very little reinforcement in tensile
strength of the resin composites.
[0049] FIGS. 5A and 5B depict two comparative fiber treatment
systems. According to the system of FIG. 5A, a fiber tow 510 is
pulled via a pulling roller 508 and is cut via a chopper (not
shown) to form 1-inch chopped fibers. The system of FIG. 5A does
not involve the use of any spreader roller such as the spreader
roller 104 of FIG. 1B or any nubbed roller such as the nubbed
roller 102 of FIG. 1A. The system of FIG. 5B includes four smooth
spreader rollers 504a, 504b, 504c, 504d placed upstream of a
pulling roller 508. The spreader rollers 504a, 504b, 504c, 504d are
to flatten a fiber tow 510, making it thinner and more flattened to
become a treated fiber tow 510 that may be chopped via a downstream
chopper (not shown). The system of FIG. 5B does not involve the use
of any nubbed rollers such as the nubbed roller 102 in FIG. 1A. The
fibers used for this comparative example are Panex 35 by Zoltek
with a 50K original tow size. The 1-inch chopped fibers may be
combined with resin paste to form composite products. It is
preferable that the resin system couples well with the chopped
fibers in order to achieve adequate fiber reinforcement for the
desired properties.
[0050] Corresponding data is recorded in FIGS. 6A1 and 6A2 and 6B1
and 6B2. FIGS. 6A1 and 6A2 show, respectively, the distributions of
width and weight of the 1-inch chopped fiber tow prepared by the
system of FIG. 5A. FIGS. 6B1 and 6B2 show, respectively,
distributions of width and weight of 1-inch chopped fiber tow
prepared by the system of FIG. 5B. The results indicate that the
rollers have flattened and spread the 50K fiber tows from the
original mean width of 8.5 millimeters (mm) to the mean width of
15.8 mm. The roller processed fiber tows, however, remain intact
with no apparent breaking-up in tow size. This is evidenced by the
almost identical mean weight of approximately 92 milligrams (mg)
and very similar weight distribution of the 1-inch chopped fibers
with and without the roller processing. The 92 mg fiber weight
corresponds to the total weight of 50,000 one inch fiber filaments
in the Panex 35 carbon fiber tows.
[0051] In comparison to the system of FIG. 5A or the system of FIG.
5B, a fiber treatment system is prepared pursuant to and as a
non-limiting example of FIG. 1C. In this example, to one of the
spreader rollers is attached or covered with a nubbed rubber sheet
that has protruding bumps mechanically penetrating and opening up
the fiber tow to form loosened or opened fiber tow. The round nubs
on the rubber sheet are approximately 3 mm in diameter and 2 mm
high, arranged approximately 8 mm apart in both x- and
y-directions. After being chopped subsequently at a chopper,
resultant distributions of width and weight of the 1-inch chopped
fiber tow are depicted in FIGS. 7A and 7B.
[0052] As depicted in FIG. 7A and 7B, the data indicate that the
mean width of the chopped fibers is 7.3 mm, as compared to 8.5 mm
for fibers processed with the system of FIG. 5A and 15.8 mm for
those processed with the system of FIG. 5B. The mean fiber weight
of the 1-inch chopped fiber tow is 43.7 mg as compared to the
original 92 mg in relation to FIGS. 5A and 5B. The weight change
indicates that the system of FIG. 1C, when coupled with a
downstream chopper, has effectively caused tow reduction in the
loosened, chopped fiber tow, say from the original 50K to two
approximately 25K tow bundles. In certain instances, non-limiting
examples of the fiber treatment system according to yet another
embodiment are depicted in FIGS. 8A and 8B.
[0053] While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
* * * * *